ABSTRACT The auto-ignition limits of propane-air mixtures at elevated pressures up to 15 bar and for concentrations from 10 mol% up to 70 mol% are investigated. The experiments are performed in a closed spherical vessel with a volume of 8 dm3. The auto-ignition temperatures decrease from 300 degrees C to 250 degrees C when increasing the pressure from 1 bar to 14.5 bar. It is shown that the fuel concentration most sensitive to auto-ignition depends on initial pressure. A second series of experiments investigates the upper flammability limit of propane-air mixtures at initial temperatures up to 250 degrees C and pressures up to 30 bar near the auto-ignition area. Finally the propane auto-oxidation is modelled using several detailed kinetic reaction mechanisms and these numerical calculations are compared with the experimental results.

[Show abstract][Hide abstract]ABSTRACT: It was found that the pure hydrogen-air pre-mixture was self-ignited at a high compression ratio without any assisting method in room temperature, thus refuting the preconception that compression ignition of hydrogen engine was impossible. Therefore, in order to analyze the correlation of compression ignition condition at cold start with hydrogen HCCI engine clearly, the possibility of compression igniting compression ratio is investigated with the change of equivalence ratio and engine speed, experimentally. As the results, it is confirmed that the possibility of compression-igniting compression ratio at cold start was decreased by increasing equivalence ratio due to decreasing auto-ignition temperature. In addition, it is grasped that the possibility of compression-igniting compression ratio at cold start is decreased around 14.9% by increasing engine speed at same supply energy.

[Show abstract][Hide abstract]ABSTRACT: The Auto-ignition temperature (AIT) is an important parameter in the process industries. In order to ensure a safe working environment in process industries, it is important to predict the AIT of combustible gases or vapors. In this study, the AITs of natural gas mixtures (CH4-Air, C3H8-Air, CH4-C3H8-Air and CH4-CO2-Air) are calculated based on a detailed kinetic model. To create a more practical model, different ignition criteria and convective heat transfer coefficients are investigated and compared against one another, resulting in the temperature criterion and a convective heat transfer coefficient of h=50 W/(m2·K). The results showed that the AITs of CH4-Air and C3H8-Air decrease with an increase of equivalence ratios. While the propane ratio increasing, the AIT of CH4-C3H8-Air decreasing. Reaction path analysis of natural gas mixtures (CH4-C3H8) was also carried out to explain this phenomenon, yielding results showing that C3H8 is the main reaction during the ignition induction period. In addition the AIT of CH4 increases slowly in positive correlation with CO2, which plays a role of an inert gas. Comparing the results with literature work revealed a deviation of about 10%. Thus, it can be reasonably concluded that the AIT of a low hydrocarbons mixtures such as natural gas can be reliably predicted with detailed kinetic model.

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